In April 2010, an explosion at the Deepwater Horizon offshore drilling rig sparked one of the biggest human-made environmental crises of all time. Over 4.9 million barrels of oil gushed into the Gulf of Mexico, leading to catastrophic damage to marine life and the wider ecosystem.

A new study has highlighted another, unexpected victim of the oil spill: Nazi submarines. Writing in the journal Frontiers in Marine Science, scientists led by the University of Southern Mississippi have detailed how the Deepwater Horizon oil spill is subjecting the area’s historical shipwrecks to more corrosive waters and causing them to disintegrate at a startling rate.

The metal of one wreck in particular, the German submarine U-166, has experienced a huge amount of corrosion. The submarine was in the Atlantic Ocean during World War II on a mission to sink merchant ships and naval vessels, an operation known as the Second Happy Time or the "American shooting season" to the Germans. U-166 sank numerous US ships during this, but the troublesome sub was eventually sunk by a depth charge in the summer of 1942 by a US ship captained by Herbert Claudius. The wreck has laid on the seabed of the Gulf of Mexico ever since and was hunted down by an archaeological survey in 2001.

Strangely enough, its recent problem with corrosion actually has its roots in bacteria living on the seafloor. The researchers argue that the influx of crude oil has provided the area’s anaerobic bacteria with carbon and sulfur to munch on. With a surplus of energy, bacterial communities have boomed and formed a dense biofilm of microorganisms that can easily stick to surfaces like a ship's hull. Unfortunately, this biofilm pumps out a corrosive by-product that can degrade metal.

To prove this, the team placed a series of carbon steel disks at historic shipwreck sites within the area affected by the Deepwater Horizon spill and others many kilometers away in “cleaner” water. The ones placed under the shadow of Deepwater Horizon were home to a much more diverse and abundant community of bacteria, including anaerobic bacteria capable of “feeding” on the carbon found in crude oil. They also documented increased metal loss in the carbon steel disks.

The researchers concede that more work is needed when it comes to understanding the interactions between biofilms, oil spills, and steel surfaces in the marine environment. However, they hope this study will provide people with a fresh, more human angle on the ongoing disaster of Deepwater Horizon.

“Given the historical and cultural significance of the U-166, we should go back,” study author Leila Hamdan told New Scientist, who first reported on the research. "The deep sea is a place that not a lot of us can connect with and this gives us a reason to care.”